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1.
A range of TeO2-P2O5 and Bi2O3-TeO2-P2O5 glass systems were prepared. The optical absorption spectra were measured in the spectral range 300–800 nm and it was found that the fundamental absorption of these glasses is dependent on the glass composition. The optical energy gap of binary glasses increases with increasing TeO2 content while the addition of Bi2O3 to TeO2-P2O5 decreases the optical energy gap. The absorption edges of these glasses arise from direct forbidden transitions and occur at photon energies in the range of 2.17 to 2.97 eV for TeO2-P2O5 glasses and 2.63 to 2.32 eV for Bi2O3-TeO2-P2O5 glasses depending on their composition.  相似文献   

2.
The infrared absorption spectra of the vitreous Co3O4-P2O5 system have been measured in the frequency region 4000 to 200 cm–1. Absorption bands and mode attributions have been fully discussed. Absorption frequencies and intensities are found to be strongly and systematically dependent on glass composition. On this basis it is found that this glass system can be divided into three distinct compositional regions. Similar three region behaviour is reported for the compositional dependence of density and molar volume of mixing of Co3O4-P2O5 glass. Quantitative justification for the band attributions has been attempted.On leave from the Physics Department, Faculty of Science, Monofia University, Shebeen El-Kome, Egypt.  相似文献   

3.
The a.c. conductivity for the TeO2-P2O5 glassy system was measured in the temperature range 300–573 K and in the frequency range 100 Hz to 10 kHz. The a.c. conductivity () increased with frequency according to the relation ()s. The frequency exponent s was found to decrease with increasing temperature. The composition dependence of the conductivity was also investigated. The density of states was also calculated using the Elliott model. The a.c. conductivity increased over the studied temperature range. The obtained experimental data have been analysed with reference to various theoretical models. The analysis shows that the correlated barrier hopping (CBH) model is the most appropriate mechanism for conduction in the TeO2-P2O5 glass system.  相似文献   

4.
Dry grinding of Ca(OH)2-P2O5 and CaO-Ca(OH)2-P2O5 mixtures was conducted by a planetary ball mill to investigate the mechanochemical solid-phase reaction for the synthesis of hydroxyapatite (Ca10(PO4)6(OH)2, HAp). HAp was synthesized by grinding of the two sets of mixtures. The formation of HAp from the Ca(OH)2-P2O5 mixture was more advantageous than that from the CaO-Ca(OH)2-P2O5 one. This synthesis reaction from the former mixture was almost completed within 30 min of grinding. The presence and amount of H2O contained in the starting mixtures played a key role to promote the formation of HAp. Especially, in the former mixture, the prolonged grinding assisted the solid-phase reaction of the intermediate DCPD and Ca(OH)2 to produce HAp more effectively.  相似文献   

5.
A series of glasses in the V2O5-P2O5 system was prepared and their compositions analysed. The glass densities and molar volumes were determined. The results obtained revealed three compositional regions. In addition, the infrared absorption spectra of these glasses were measured at room temperature in the frequency range 1600–200 cm–1. The compositional dependence of the bands present, attributed to a given band and mode of vibration, was investigated. However, the infrared data confirmed the results obtained from the density and molar volume measurements.  相似文献   

6.
The crystal line phases Me2O·V2O5·2TeO2 (Me=Li, Na, K, Cs, Ag) and their glasses are studied with the aid of infra-red spectroscopy. The radial distribution function (RDF) curves of two glasses, Na2O·V2O5·2TeO2 and Cs2O·V2O5·2TeO2, are obtained by an X-ray diffraction study. An attempt is made to identify the main bands in the infra-red spectra of the crystalline compounds and the glasses. The absorption bands in the 970 to 880 cm–1 range are assigned to the stretching modes of the VO2 isolated groups. A trend is observed towards a shift of the high-frequency band by the replacement of an alkaline ion with another in the order Ag+, Cu+, Li+, Na+, K+, Rb+, Cs+, which is explained by their different polarizing ability. With the aid of X-ray diffraction studies it is shown that the basic structure units in the glasses studied are the VO4 and TeO4 groups.  相似文献   

7.
Glassy solids of the system Al2O3-P2O5-SiO2, which have not been obtainable because of the devitrification of glass during the cooling process after melting, were obtained by the gel method. After the gels of the system Al2O3-P2O5-SiO2 were prepared from AlCl3·6H2O, H3PO4 and Si(OC2H5)4, they were heat treated up to 800° C to obtain glassy solids. In SiO2 concentrations ranging from 75 to 82 mol % in batch compositions, non-porous transparent solids were obtained, while in SiO2 concentrations above 87 mol %, porous transparent solids were obtained. Tridymite was precipitated because of the crystallization of glassy solids during heat treatment above 800° C. It depended upon the microstructure of the gels whether non-porous glassy solids were obtained or not. The thermal expansion coefficients of the glassy solids were greatly dependent upon the concentration of P2O5, ranging from 1.7×10−6 to 4.2×10−6 (1/° C).  相似文献   

8.
The co-effects of two glass-formers in the TeO2-P2O5 system are studied on the basis of neutron diffraction data. The curves for the radial distribution function (RDF) obtained show a high extent of destruction of the short-range order in the tellurite matrix, while the basic co-ordination PO4 polyhedron remains unchanged. The co-ordination number (cn) of the Te atom changes from 4 to 3+1 and marked tendency towards elongation of the Te-O distances over 2.3 Å is observed. The considerably higher stability of the PO4 polyhedra and their strong influence on the TeO4 polyhedra is established. The observed smearing effect of the Te-Te, Te-second O and O-second O distances in the range of 3.8 to 3.9 Å in other tellurite glasses is also characteristic of this system. A structural interpretation of the liquid-liquid immiscibility on the short-range order level in the system is given. A critical composition with 26±5% of the second glass-former is established, above which concentration a stable immiscibility in the tellurite systems is observed. An attempt is made to construct two adequate structural models (microhomogeneous and microheterogeneous) for the short-range order in the glasses studied.  相似文献   

9.
The phase equilibria and immiscibility of mutual glass formers up to 50 mol% P2O5 have been studied. Phase analysis indicates the formation of three new phases — incongruent melting Te4P2O13, Te2P2O9, and a supposed metacompound. Electron microscope investigations established stable and metastable phase separation. The immiscibility confines the tendency to glass formation up to 25.8 mol % P2O5. A reliable interpretation in relation to the morphology of liquid-liquid immiscibility and crystallization is considered.  相似文献   

10.
Thin SiO2-P2O5-CaO films have been produced by a sol-gel process from film-forming solutions. The physicochemical processes underlying the formation of the films have been investigated, and their phase composition, structure, and bioactivity have been determined.  相似文献   

11.
The influence of ZnO substitution by 0–12 wt.% Na2O on the properties of ZnO-Sb2O3-P2O5-Na2O glasses has been investigated. The structure and properties of the glasses with the composition of (13.86-x)ZnO-57.93Sb2O3-28.21P2O5?x Na2O (x = 0–12 wt.%) were characterized by infrared spectra (IR), X-ray diffraction and differential thermal analysis (DTA). The results of IR indicated an increase in the intensity of symmetric vibrations of P-O-P bond, which was confirmed by the improvement of water durability with the increasing amount of Na2O in the range of 0–10 wt.%. Substitution of 10 wt.% Na2O led to the weight loss of the glass to 5.93 mg/cm?2 after immersion in deionized water at 50 °C for 24 h. The results of XRD showed that the ability of crystallization decreased, indicating the good thermal stability of the glass. The glass containing 8 wt.% Na2O had the best properties in every respect and might be an alternative to lead based glasses for the applications, providing further composition improvement.  相似文献   

12.
A study of TeO2–P2O5 glass system has been carried out by Differential Thermal Analysis (DTA) to elucidate the kinetics of crystallization for these glassy samples. The results of DTA performed at different heating rates are discussed. The values of the glass transition temperature, T g , as well as the glass crystallization temperature, T c , are found to be dependent upon the heating rate. From this dependence, the values of activation energy for both the glass transition and crystallization are evaluated and discussed  相似文献   

13.
The Fourier transform infrared spectra of different compositions of evaporated V2O5/B2O3 thin films have been investigated. Most of the absorption bands corresponding to V2O5 and B2O3 films coincide with those reported by other authors. The short-range order in amorphous V2O5 films is found to be conserved. The absorption spectra indicate a boroxol ring structure for B2O3 films. In co-evaporated V2O5/B2O3 films the boron is observed to substitute in the V2O5 network such that the coordination number of vanadium ion remains unchanged. The presence of a number of bands corresponding to -OH groups indicates the hygroscopic character of the films.  相似文献   

14.
Mixtures of CaO-SiO2-P2O5-CaF2 glass powders with 3.7 m ammonium phosphate solution give bioactive cements which can set in a few minutes and bond to living bone in a few weeks. In the present study, the mechanical strengths of the mixtures, which were held in 100% humidity at 37°C for 1 h and then soaked in a simulated body fluid (SBF) for 23 h, were investigated in terms of the glass composition. Their compressive strengths varied significantly with small changes in the CaO/SiO2/P2O5 ratios under a constant CaF2 content. Addition of CaF2 to a CaO-SiO2-P2O5 composition increased the compressive strength, whereas addition of MgO decreased it. The glass composition of CaO 47.1, SiO2 35.8, P2O5 17.1, CaF2 0.75 wt ratio gave the highest compressive strength among the compositions examined: 56 and 80 MPa, respectively, after soaking in the simulated body fluid for 23 h and 3 days. The variation of the compressive strength with the glass composition was well interpreted in terms of the amount of the hydroxyapatite formed at the intergranular spaces of the glass powders in the simulated body fluid.  相似文献   

15.
X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass containing different amounts of iron ranging from 0–7.5 mol % and heat treated at 300 °C for various times. The structure and phase separation could be determined for each glass composition. V2O5 was the main precipitated phase in all heat-treated samples, and its amount was dependent on the heat-treatment time and Fe2O3 content. Also FeP was detected in samples heat treated for 24 h. The infrared measurements showed the presence of both V4+ and V5+. The symmetry of V2O 7 4− and VO 4 3− groups was found to increase with increasing Fe2O3 content. It was also found that some PO4 changed to BO3, forming a non-bridging oxygen.  相似文献   

16.
The optical absorption and the esr spectra of titanium(III) in binary Na2O-B2O3 and Na2O-P2O5 glasses have been studied. Titanium(III) produces two optical absorption bands around 20 000 and 14 000 cm–1 which are assigned to the2B2g 2B1g and2B2g 2A1g transitions respectively of Ti3+ in a tetragonally distorted octahedral environment. The absorption bands in phosphate glasses are narrower and absorption coefficients higher than those in borate glasses. The esr spectrum of titanium(III) in all the glasses consists of a broad asymmetric line withg 1.94 in borate glasses, andg 1.92 in phosphate glasses; no hyperfine structure has been observed.  相似文献   

17.
The optical absorption spectra of evaporated V2O5 and co-evaporated V2O5/B2O3 thin films have been studied. For higher photon energies, the absorption is found to be due to a direct forbidden electronic transition process from the oxygen 2p band to the vanadium 3d band in a similar way to that observed in crystalline V2O5. The exponential behaviour of absorption edge for lower photon energies is attributed to the electronic transitions between the tailed-off d-d states corresponding to V4+ ions. For co-evaporated V2O5/B2O3 films the optical energy gap is observed to increase with the increase in V2O5 content of the composite films.  相似文献   

18.
 The patterns of hydrating and solidifying with the compositional variation of phosphorus-rich, phosphorus-calcium-rich and aluminum-calcium rich regions in ternary system CaO-Al2O3-P2O5 has been studied in detail, and two new ternary compounds L and H have been synthesized here. The results indicate that the region of 48–56% P2O5 doesn’t present cementitiousness, which contains mainly crystal phases of β-C2P(2CaO·P2O5), α-C3P(3CaO·P2O5) and AlPO4; the phosphorus-calcium-rich region of 21–35% P2O5 exhibits substantial cementitiousness, which contains mainly crystal phase of α-C3P and certain amount of CA(CaO·Al2O3) and new phases L/H; and the aluminum-calcium-rich region of 8–18% P2O5 is full of promise for cementitiousness. It contains mainly new crystal phase L and certain amount of α-C3P and CA. The hydration and solidification mechanisms have been preliminarily analyzed by means of XRD, XPS and DTA. It appears that crystal phase CA might hydrate directly to the stable phase of C3A·6H2O in the phosphorus-rich case of 21–35% P2O5; new phase H has the behavior of rapid setting; and L, being a dominant phase, can prevent cement pastes from significant strength loss in long curing cycles. Received: 12 March 1998 / Accepted: 29 July 1998  相似文献   

19.
The d.c. and a.c. electrical properties on TeO2-Fe2O3 glasses with various compositions of PbO, B2O3 and SiO2 were studied over a frequency range of 102–105 Hz and in the temperature range 300–500 K. The a.c. conductivity is proportional tow n, and the conduction mechanism is due to an electronic hopping process. The effects of composition and temperature on the dielectric constant and loss factor (tan ) were studied. The infrared absorption spectra of these glasses reveal that the addition of PbO, B2O3 and SiO2 of these glasses does not introduce any new absorption band in the infrared spectrum of TeO2-Fe2O3 glasses. These results prove the distribution of TeO4 polyhedra which determines the network and basic oscillation of the building units in the tellurite glasses.  相似文献   

20.
A study of glasses from the ternary system CaF2-CaAl2Si2O8-P2O5 has been carried out. It has been shown that glasses with low phosphorus contents and high fluorite contents crystallise to fluorite. Fluorine reduces the glass transition temperature and is also required for the formation of fluorapatite (FAP). In the absence of fluorine in the glass no apatite phase is formed. Bulk nucleation of FAP is favoured for glasses with Ca:P ratios close to the apatite stoichiometry of 1.67 and with low crosslink densities. Thermal gravimetric analysis showed significant weight losses attributable to the formation of volatile silicon tetrafluoride to occur on crystallisation of the aluminium containing phases, anorthite and mullite, which supports the view that silicon tetrafluoride formation is hindered by fluorine bonding to the aluminium atoms of the glass network. Anorthite crystallisation always occurred by a surface nucleation mechanism and appeared to be favoured by the higher silicon to aluminium ratio in these glasses compared to previously studied glass compositions.  相似文献   

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